mt76: connac: move mt76_connac2_load_ram in connac module

Move mt76_connac2_load_ram utility routine in mt76_connac module since
it is shared between mt7921 and mt7915. This is a preliminary patch to
support mt7902e driver.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>